Heretofore, in a coating system for coating an article(s) to be coated (hereinafter referred to as a work(s)) such as an automobile bodies, since coating at high quality is required, electrostatic coating machine excellent in the deposition efficiency and the smoothness of coating layer has been used.
In the electrostatic coating machine, a rotary atomizing head for atomizing an aqueous coating material for electrostatic coating is provided, and by application of high voltage to the rotary atomizing head, coating material particles atomized in the rotary atomizing head are charged and electrostatic coating is conducted.
The electrostatic coating machine includes a coating machine in which a coating material cartridge is mounted to a coating machine main body and a predetermined amount of a liquid for pumping out a coating material (hereinafter referred to as a hydraulic fluid) is filled thereby pumping out the coating material in the coating material cartridge and supplying the same to the rotary atomizing head to conduct coating (refer, for example, to Patent Citation 1).
The coating material cartridge has a coating material chamber and a hydraulic fluid chamber partitioned from each other by way of a partition, in which a coating material in the coating material chamber is pumped out along with movement of a piston after filling the hydraulic fluid.
By the way, since an electric current could leak by way of a coating material flowing through a coating material supply system, an insulation countermeasure for preventing this is necessary. As the countermeasure, there has been proposed, for example, to use an insulating solution (organic solvent or the like) as the hydraulic fluid.
The hydraulic fluid is a fluid having a specific gravity as low as from 0.7 to 0.9, and with a reduced weight compared with an aqueous coating material for use in electrostatic coating having a specific gravity from 1.1 to 1.3.
Further, as another insulation countermeasure, it has been proposed to mount a coating material cartridge 100 having a coating material bag 101 filled with a coating material (refer to FIG. 7) to a coating machine main body instead of an existent coating material cartridge. By the use of the coating material cartridge 100, since coating material leakage from the inside of the coating material chamber 102 (inside of the coating material bag 101) to the hydraulic fluid chamber 103 is prevented completely, current leakage can be prevented more reliably. In this case, the coating material is supplied to a rotary atomizing head by filling the hydraulic fluid into the hydraulic fluid chamber 103 and pumping out the coating material in the coating material bag 101. The coating material cartridge 100 is mounted not only to the coating machine but also to a coating material filling device 110 (refer to FIG. 7). The coating material filling device 110 fills a coating material in the coating material chamber 102 when the coating material cartridge 100 is mounted.
Further, in the coating material cartridge described in the Patent Citation 1, since the coating material chamber occupies a lower region of a piston and the hydraulic fluid chamber occupies an upper region of the piston, an opening of a hydraulic fluid transfer path 104 for supplying and charging the hydraulic fluid to the hydraulic fluid chamber is disposed in an upper portion of the coating material cartridge 100. Further, also in a coating material cartridge 100 in which the piston is replaced with the coating material bag 101, the opening of the hydraulic fluid transfer path 104 is disposed in an upper portion of the coating material cartridge 100.
[Patent Citation 1] JP-A No. 2000-176328 (refer to FIG. 1, etc.)